Update IstanbulJS and add compatibility to the PR #99

[SimonSimCity]

In the IstanbulJS API package, the transformer-method https://github.com/istanbuljs/istanbuljs/pull/99/files#diff-e0c7058aa9756c4cb034603b8e01b783R57 required some changes. Likewise this package will have to adapt to the new call of the runInThisContext() method. This is a simple way to support both the old and the new variant.

This will fix the error mentioned in #54 (comment)

[coveralls]

Coverage remained the same at 78.0% when pulling 49ae8d8 on SimonSimCity:feature/update-lib-istanbul into 2bdb456 on serut:bugfix/repair-tests.

[SimonSimCity]

After istanbuljs/istanbuljs#99 has been approved this PR can safely be merged. It is also backwards compatible to older versions of Meteor, where runInThisContext() was called in the old way.

[serut]

Looks like istanbuljs have merged that pull request. All these PR will be merged asap.
Thanks for your huge investment @SimonSimCity !

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@fd36541). Click here to learn what that means.
The diff coverage is n/a.

@@          Coverage Diff           @@
##             master   #60   +/-   ##
======================================
  Coverage          ?   78%           
======================================
  Files             ?     1           
  Lines             ?    50           
  Branches          ?     0           
======================================
  Hits              ?    39           
  Misses            ?    11           
  Partials          ?     0

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[SimonSimCity]

I've updated the package as described in istanbuljs/istanbuljs#143 and can confirm that this branch now works without any further modifications on Meteor 1.6.1 🎉